From 6fedb7aa0f76c34bccedd14095bcc7824006489d Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Fri, 14 Nov 2008 15:46:45 +0000
Subject: [PATCH] * Restore SIGPIPE to SIG_DFL when running the builder.  This
 prevents   subtle and often hard-to-reproduce bugs where programs in pipes  
 either barf with a "Broken pipe" message or not, depending on the   exact
 timing conditions.  This particularly happened in GNU M4 (and   Bison, which
 uses M4).

---
 src/libstore/build.cc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 436cf4762d..a1c99cddd0 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -361,6 +361,15 @@ const char * * strings2CharPtrs(const Strings & ss)
 }
 
 
+/* Restore default handling of SIGPIPE, otherwise some programs will
+   randomly say "Broken pipe". */
+static void restoreSIGPIPE() 
+{
+    struct sigaction act, oact;
+    act.sa_handler = SIG_DFL;
+    act.sa_flags = 0;
+    if (sigaction(SIGPIPE, &act, &oact)) throw SysError("resetting SIGPIPE");
+}
 
 
 //////////////////////////////////////////////////////////////////////
@@ -514,6 +523,8 @@ static void runSetuidHelper(const string & command,
             args.push_back(arg.c_str());
             args.push_back(0);
 
+            restoreSIGPIPE();
+            
             execve(program.c_str(), (char * *) &args[0], 0);
             throw SysError(format("executing `%1%'") % program);
         }
@@ -1878,6 +1889,8 @@ void DerivationGoal::startBuilder()
                 args.push_back(i->c_str());
             args.push_back(0);
 
+            restoreSIGPIPE();
+
             /* Execute the program.  This should not return. */
             execve(program.c_str(), (char * *) &args[0], (char * *) envArr);